Geochemical behavior of heavy metals and radionuclides in a pit lake affected by acid mine drainage (AMD) in the Muskau Arch (Poland).

Pit lakes in the 'anthropogenic lake district' in the Muskau Arch (western Poland; central Europe) are strongly affected by acid mine drainage (AMD). The studied acidic pit lake, ŁK-61 (pH <3), is also exposed to floods due to its location in the flood hazard area, which may significantly influence the geochemical behavior of elements. The elemental compositions of water and lake sediment samples were measured with ICP-OES and ICP-MS.

Alpha radiation from polymetallic nodules and potential health risks from deep-sea mining.

In search for critical elements, polymetallic nodules at the deep abyssal seafloor are targeted for mining operations. Nodules efficiently scavenge and retain several naturally occurring uranium-series radioisotopes, which predominantly emit alpha radiation during decay. Here, we present new data on the activity concentrations of thorium-230, radium-226, and protactinium-231, as well as on the release of radon-222 in and from nodules from the NE Pacific Ocean.

Deglacial patterns of South Pacific overturning inferred from Pa and Th.

The millennial-scale variability of the Atlantic Meridional Overturning Circulation (AMOC) is well documented for the last glacial termination and beyond. Despite its importance for the climate system, the evolution of the South Pacific overturning circulation (SPOC) is by far less well understood. A recently published study highlights the potential applicability of the Pa/Th-proxy in the Pacific.

Glacial episodes of a freshwater Arctic Ocean covered by a thick ice shelf.

Following early hypotheses about the possible existence of Arctic ice shelves in the past, the observation of specific erosional features as deep as 1,000 metres below the current sea level confirmed the presence of a thick layer of ice on the Lomonosov Ridge in the central Arctic Ocean and elsewhere. Recent modelling studies have addressed how an ice shelf may have built up in glacial periods, covering most of the Arctic Ocean. So far, however, there is no irrefutable marine-sediment characterization of such an extensive ice shelf in the Arctic, raising doubt about the impact of glacial conditions on the Arctic Ocean.

Coastal ocean and shelf-sea biogeochemical cycling of trace elements and isotopes: lessons learned from GEOTRACES.

Continental shelves and shelf seas play a central role in the global carbon cycle. However, their importance with respect to trace element and isotope (TEI) inputs to ocean basins is less well understood. Here, we present major findings on shelf TEI biogeochemistry from the GEOTRACES programme as well as a proof of concept for a new method to estimate shelf TEI fluxes.

Pacific Proving Grounds radioisotope imprint in the Philippine Sea sediments.

Radionuclide concentrations were studied in sediment cores taken at the continental slope of the Philippine Sea off Mindanao Island in the equatorial Western Pacific. High resolution deposition records of anthropogenic radionuclides were collected at this site. Excess Pb together with excess Th and anthropogenic radionuclides provided information about accumulation rates.

Response to Comment on "Dissolved organic sulfur in the ocean: Biogeochemistry of a petagram inventory".

Dittmar proposed that mixing alone can explain our observed decrease in marine dissolved organic sulfur with age. However, their simple model lacks an explanation for the origin of sulfur-depleted organic matter in the deep ocean and cannot adequately reproduce our observed stoichiometric changes. Using radiocarbon age also implicitly models the preferential cycling of sulfur that they are disputing.

Dissolved organic sulfur in the ocean: Biogeochemistry of a petagram inventory.

Although sulfur is an essential element for marine primary production and critical for climate processes, little is known about the oceanic pool of nonvolatile dissolved organic sulfur (DOS). We present a basin-scale distribution of solid-phase extractable DOS in the East Atlantic Ocean and the Atlantic sector of the Southern Ocean. Although molar DOS versus dissolved organic nitrogen (DON) ratios of 0.

Inorganics in organics: quantification of organic phosphorus and sulfur and trace element speciation in natural organic matter using HPLC-ICPMS.

A method is presented for the chemical characterization of natural organic matter (NOM). We combined reversed-phase chromatographic separation of NOM with high resolution inductively coupled plasma mass spectrometry. A desolvation technique was used to remove organic solvent derived from the preceding chromatographic separation.

Southern Ocean dust-climate coupling over the past four million years.

Dust has the potential to modify global climate by influencing the radiative balance of the atmosphere and by supplying iron and other essential limiting micronutrients to the ocean. Indeed, dust supply to the Southern Ocean increases during ice ages, and 'iron fertilization' of the subantarctic zone may have contributed up to 40 parts per million by volume (p.p.